SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Spectrophotometry

169

BACKGROUND: The new combination of moxifloxacin HCl and cefixime trihydrate is approved for the treatments of lower respiratory tract infections in adults. At initial formulation development and screening stage a fast and reliable method for the dissolution and release testing of moxifloxacin and cefixime were highly desirable. The zero order overlaid UV spectra of moxifloxacin and cefixime showed >90% of spectra are overlapping. Hence, simple, accurate precise and validated two derivative spectrophotometric methods have been developed for the determination of moxifloxacin and cefixime. METHODS: In the first derivative spectrophotometric method varying concentration of moxifloxacin and cefixime were prepared and scanned in the range of 200 to 400 nm and first derivative spectra were calculated (n = 1). The zero crossing wavelengths 287 nm and 317.9 nm were selected for determination of moxifloxacin and cefixime, respectively. In the second method the first derivative of ratio spectra was calculated and used for the determination of moxifloxacin and cefixime by measuring the peak intensity at 359.3 nm and 269.6 nm respectively. RESULTS: Calibration graphs were established in the range of 1–16 mug /mL and 1–15 mug /mL for both the drugs by first and ratio first derivative spectroscopic methods respectively with good correlation coefficients. Average accuracy of assay of moxifloxacin and cefixime were found to be 100.68% and 98 93%, respectively. Relative standard deviations of both inter and intraday assays were less than 1.8%. Moreover, recovery of moxifloxacin and cefixime was more than 98.7% and 99.1%, respectively. CONCLUSIONS: The described derivative spectrophotometric methods are simple, rapid, accurate, precise and excellent alternative to sophisticated chromatographic techniques. Hence, the proposed methods can be used for the quality control of the cited drugs and can be extended for routine analysis of the drugs in formulations.

Concepts: Spectroscopy, Ultraviolet, Respiratory system, Upper respiratory tract, Accuracy and precision, Lower respiratory tract, Ultraviolet-visible spectroscopy, Spectrophotometry

167

Background and the purpose of the study: Rizatriptan is used effectively for the treatment of migraine headache. In this study, a simple, rapid and low cost spectrophotometric method based on the ion-pair complexation is proposed for the determination of rizatriptan in raw material and dosage forms. METHODS: The ion-pair complexation using bromocresol green as reagent was performed in a buffer solution and the absorbance was measured by a spectrophotometer. The ion-pair formation conditions were optimized and the accuracy and precision of the method were calculated.Results and major conclusion: Best results were achieved by using 6 ml of the bromocresol green reagent in the presence of phosphate buffer (pH 3.0). The stoichiometry of the resulted complex was 1:1. The within-day and between-day precision values were lower than 2.9 and 1.8 percent for the calibration range of 0.5–50 and 10–100 mug/ml, respectively. The proposed method was successfully used for the determination of rizatriptan in dosage forms without any interference.

Concepts: Spectroscopy, Chemical equilibrium, PH, Phosphate buffered saline, Accuracy and precision, Buffer solution, Equilibrium chemistry, Spectrophotometry

8

We have developed disposable color-changing polymeric films for quantification of furfural, -a freshness indicator-, in beer using a smartphone-based reader. The films are prepared by radical polymerization of 4-vinylaniline, as furfural-sensitive indicator monomer, 2-hydroxymethylmethacrylate as co-monomer and ethylene dimethylmethacrylate (EDMA) as cross-linker. The sensing mechan ism is based on the Stenhouse reaction in which aniline and furfural react in acidic media with generation of a deep red cyanine derivative, absorbing at 537 nm, which is visible to the naked eye. The colorimetric response has been monitored using either a portable fiber-optic spectrophotometer or the built-in camera of a smartphone. Under the optimized conditions, a linear response to furfural in beer was obtained in the 39 to 500 µg L(-1) range, with a detection limit of 12 µg L(-1), thus improving the performance of other well-established colorimetric or chromatographic methods. The novel films are highly selective to furfural and no cross-reactivity has been observed from other volatile compounds generated during beer ageing. A smartphone application (app), developed for Android® platforms, measures the RGB color coordinates of the sensing membranes after exposure to the analyte. Following data processing, the signals are converted into concentration values by pre-loaded calibration curves. The method has been applied to determination of furfural in ale beers with different storage times at room temperature. A linear correlation (r > 0.995) between the storage time and the furfural concentration in the samples has been confirmed; our results have been validated by HPLC with diode-array detection.

Concepts: Polymer, Polymer chemistry, Analytical chemistry, Color, Monomer, Polymerization, Spectrophotometry, Colorimetry

2

Limonium brasiliense is a common plant on the southern coast of Brazil. The roots are traditionally used for treatment of premenstrual syndrome, menstrual disturbances and genito-urinary infections. Pharmaceutical preparations obtained from its roots and used for these purposes were marketed in Brazil in the 1980s and 1990s. Currently, the Brazilian Drug Agency (National Health Surveillance Agency, ANVISA) has canceled the registration of these products, and their use was discontinued because of a lack of studies to characterize the plant raw material and ensure the effectiveness and safety of its use. The aim of the present study was to develop and validate an analytical method to determine the content of total polyphenols (TP) in an extract from L. brasiliense roots, by the UV/Vis spectrophotometric method. L. brasiliense roots were extracted in acetone:water (7:3, v/v-10% w/v). The crude extract was used to develop a method for TP assay. The method was validated according to national and international guidelines. The optimum conditions for analysis time, wavelength, and standard substance were 30 min, 760 nm, and pyrogallol, respectively. Under these conditions, validation by UV/Vis spectrophotometry proved the method to be linear, specific, precise, accurate, reproducible, robust, and easy to perform. This methodology complies with the requirements for analytical application and to ensure the reliability of the results.

Concepts: Scientific method, Spectroscopy, Validation, Accuracy and precision, Standard, The Roots, Spectrophotometry, Premenstrual syndrome

1

For birds, plumage color perception is critical in social interactions such as courtship, in both monochromatic and dichromatic species. In the Eared Dove (Zenaida auriculata), perhaps the most abundant South American Columbiforme, the plumage of males and females looks alike and both sexes share the same melanistic coloration with gray and pink tones. The aim of this study was therefore to determine whether evident sexual dichromatism exists in the plumage of the Eared Dove using a spectrophotometry technique in the avian-visible range (300-700 nm). The results of the classic colorimetric variables analysis (hue, chroma and brightness) show that males are in general brighter and have higher UV chroma values than females. The avian visual model points to differences in achromatic and chromatic levels between males and females in body regions possibly involved in sexual selection (e.g. the crown). The model also indicates chromatic or achromatic differences in body regions not subject to sexual selection such as the black spots on the wing coverts and white tail bands, both of which may be involved in intra- or inter-gender-specific communication.

Concepts: Sexual dimorphism, Sociology, Bird, Sex, Color, Spectrophotometry, Socorro Dove, Eared Dove

0

In the present study, a new preconcentration method was developed to quantify the free formaldehyde (FA) in hair cosmetics by combining ultrasound-assisted cloud-point extraction with spectrophotometry. The method is based on the ion association of FA with cationic phenothiazine group dye, toluidine blue in presence of sulfite at pH 5.0, and then extraction of the formed complex into the micellar phase of nonionic surfactant, Triton X-114. The analyte extracted into the micellar phase was diluted with ethanol, and then detected at 630 nm by spectrophotometer. Under optimal conditions, a good linear relationship was obtained in the range of 2-120 μg/L with a detection limit of 0.38 μg/L. By preconcentration of 15 mL sample, the calibration sensitivity increased by 74-fold. The intra- and inter-day precisions expressed as RSDs are lower than 4.7 and 5.2%, respectively. Compared with other techniques, the study shown here provides a simple, fast, accurate, and reliable method for the analysis of FA in cosmetic products. The contents of FA of the samples are in the range of 3.4-25.1 mg/kg with an RSD lower than 4.6%. The results were statistically in good agreement with those obtained by an independent comparison method. Highlights: A new method was developed for the preconcentration of free formaldehyde from hair cosmetics. The method is simple, fast, precise, selective, and sensitive to detect trace formaldehyde. The precision is lower than 5.2% with recovery higher than 95% after spiking. The method was validated by comparing the results with those of independent method. The formaldehyde levels of hair cosmetics were reliably monitored and determined.

Concepts: Ultraviolet, Method acting, Ion, Surfactant, Accuracy and precision, Cosmetics, Extraction, Spectrophotometry

0

Accurate measurements of reflectance and color require spectrophotometers with prices often exceeding $3000. Recently, new “color instruments” became available with much lower prices, thanks to the availability of inexpensive colorimetric sensors. We investigated the Node+ChromaPro and the Color Muse, launched in 2015 and 2016 by Variable Inc. Both instruments are colorimeters, combining a colorimetric sensor with LED lighting. We investigated color accuracy compared to a high-end spectrophotometer from BYK Gardner. With different sets of samples we find for the Node an average value of dECMC (1:1) = 1.50, and a maximum of 7.86, when comparing with the 45° geometry of the spectrophotometer. Utilizing measurement data on the Spectral Power Distributions of the LEDs, we developed three methods to improve color accuracy as compared to the spectrophotometer data. We used these methods on different sets of samples with various degrees of gloss, both for training the models underlying the methods and for independent tests of model accuracy. Average color accuracy of the Node+ChromaPro improves from dECMC (1:1) = 1.82 to 1.16 with respect to spectrophotometer data. The percentage of samples with dECMC (1:1) < 1.0 increases from 30.9% (uncorrected) to 64%. With the improved color accuracy, these sensors become useful for many more applications.

Concepts: Better, Improve, Measurement, Color, Light-emitting diode, Lighting, Spectrophotometry, Colorimetry

0

Anthocyanins and norbixin are natural pigments used in food; however, they are unstable. The aim of this study was to evaluate the microencapsulation technique to protect these pigments. Elderberry extract (source of anthocyanins) and norbixin were encapsulated using a microfluidic device with palm oil as middle phase in a water-in-oil-in-water emulsion. The formulations were characterized for morphology, particle size, encapsulation efficiency, zeta potential, color release under heating, Fourier transform infrared spectrophotometry, and color stability under different conditions. Spherical, mononucleated microcapsules, with particle size of 187-190 μm (elderberry) and 164-184 μm (norbixin), and with encapsulation efficiencies values of 47.80-54.87% (elderberry) and 49.18-74.73% (norbixin) were obtained. The formulations showed high color retention, with the encapsulated elderberry extract stored at pH 3.0 being the most stable. This study shows that the microencapsulation of these pigments using a microfluidic device provided protection, and represents a new method for anthocyanins and norbixin delivery in foods.

Concepts: Spectroscopy, Nuclear magnetic resonance, Surface tension, Fourier transform, Infrared spectroscopy, Fourier transform spectroscopy, Fourier analysis, Spectrophotometry

0

In this study mango kernel starch (MKS) based heat sealable pouches were developed for packing of red chili powder. The films were prepared by casting technique using glycerol, sorbitol and 1:1 mixture of glycerol and sorbitol and were sealed. All films showed better heat sealing capacity but glycerol films plasticized exhibited higher seal strength than their counterparts. The red chili powder was packed in the MKS film pouches while commercially available polyethylene (PE) film was used as control. The pungency and color of red chili powder was monitored during six months storage at 40 °C. The capsaicinoid content was extracted from the red chili with acetonitrile and evaluated quantitatively using spectrophotometric method. The extractable color was measured by ASTA method using acetone. The results showed significant differences in color and pungency of chili packed in MKS and PE pouches. The highest reduction in capsaicinoid content (pungency) of chili powder was observed in PE pouch (25.9%) while lowest was observed in MKS pouch containing sorbitol (15.7%). Similarly color loss was also highest in chili packed in PE pouch while lowest in MKS-sorbitol pouch.

Concepts: Glucose, Pinniped, Capsicum, Capsaicin, Chili pepper, Spectrophotometry, Cayenne pepper, Chili powder

0

α-Viniferin and caraphenol A, the two oligostilbenes, have the sole difference of the presence or absence of an exocyclic double bond at the π-π conjugative site. In this study, the antioxidant capacity and relevant mechanisms for α-viniferin and caraphenol A were comparatively explored using spectrophotometry, UV-visible spectral analysis, and electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) analysis. The spectrophotometric results suggested that caraphenol A always gave lower IC50values than α-viniferin in cupric ion-reducing antioxidant capacity assay, ferric-reducing antioxidant power assay, 1,1-diphenyl-2-picryl-hydrazl radical (DPPH•)-scavenging, and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical-scavenging assays. In UV-visible spectra analysis, caraphenol A was observed to show enhanced peaks at 250-350 nm when mixed with Fe2+, but α-viniferin exhibited no similar effects. UPLC-ESI-Q-TOF-MS/MS analysis revealed that α-viniferin mixed with DPPH• produced radical adduct formation (RAF) peak (m/z= 1070-1072). We conclude that the antioxidant action of α-viniferin and caraphenol A may involve both redox-mediated mechanisms (especially electron transfer and H⁺-transfer) and non-redox-mediated mechanisms (including Fe2+-chelating or RAF). The π-π conjugation of the exocyclic double bond in caraphenol A can greatly enhance the redox-mediated antioxidant mechanisms and partially promote the Fe2+-chelating mechanism. This makes caraphenol A far superior to α-viniferin in total antioxidant levels.

Concepts: Spectroscopy, Mass spectrometry, Antioxidant, Electrospray ionization, Taylor cone, Tandem mass spectrometry, Spectrophotometry, Time-resolved spectroscopy